U.S. patent application number 12/090337 was filed with the patent office on 2009-06-11 for arrangement for telescopic fork leg with parallel damping.
This patent application is currently assigned to Ohlins Racing AB. Invention is credited to Torkel Sintorn.
Application Number | 20090145706 12/090337 |
Document ID | / |
Family ID | 37569289 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090145706 |
Kind Code |
A1 |
Sintorn; Torkel |
June 11, 2009 |
ARRANGEMENT FOR TELESCOPIC FORK LEG WITH PARALLEL DAMPING
Abstract
A device for telescopic fork legs, preferably for a motorcycle
or bicycle. The device is a compact removable unit that comprises
parallel medium flow passages that run between upper and lower
sides of the piston. This unit that is simple to adapt to different
front fork dimensions and to use as a kit for providing an existing
front fork with parallel damping. Parallel damping achieves simple
adaptation of the damping characteristics to different types of
terrain.
Inventors: |
Sintorn; Torkel; (Vaxholm,
SE) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Ohlins Racing AB
Upplands Vasby
SE
|
Family ID: |
37569289 |
Appl. No.: |
12/090337 |
Filed: |
October 18, 2006 |
PCT Filed: |
October 18, 2006 |
PCT NO: |
PCT/SE06/01187 |
371 Date: |
September 24, 2008 |
Current U.S.
Class: |
188/266.2 |
Current CPC
Class: |
F16F 9/062 20130101;
F16F 9/065 20130101; B60G 17/08 20130101; B60G 17/04 20130101; B60G
2500/11 20130101; B60G 2500/20 20130101; B60G 2300/12 20130101;
B60G 15/061 20130101; B62K 25/08 20130101; F16F 9/46 20130101; B60G
2202/154 20130101 |
Class at
Publication: |
188/266.2 |
International
Class: |
F16F 9/512 20060101
F16F009/512 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2005 |
SE |
0502310-6 |
Claims
1-9. (canceled)
10. A removable insert device for telescopic fork legs that
comprise outer and inner legs and a damping system with a piston
and piston rod arrangement arranged within a region defined at
least in part by the outer and inner legs, the device comprising:
two generally concentric tubes, a first medium flow passage defined
between the two generally concentric tubes; a second medium flow
passage and a third medium flow passage extending in parallel to
each other and extending between an upper side of the piston and a
lower side of the piston; the second medium flow passage and the
third medium flow passage being fluidly coupled to the first medium
flow passage and running parallel in relation to each other, and a
pressurizing member in fluid communication with the second and
third medium flow passage; the first and second medium flow
passages each comprising flow control devices that are configured
to adjust the damping characteristics of the fork legs to different
types of terrain.
11. The device of claim 10 in combination with a vehicle.
12. The device of claim 10 in combination with a motorcycle.
13. The device of claim 10, wherein a tube end is mounted to a
first end of the two generally concentric tubes and a head is
mounted to a second end of the two generally concentric tubes, the
head also being coupled to the outer leg of the fork legs.
14. The device of claim 13, wherein the piston rod is sealed
against and extends through the tube end.
15. The device of claim 13, wherein a first end of the piston rod
is attached to a bottom unit, the bottom unit being connected to
the inner leg, the piston being attached to a second end of the
piston rod, and the piston being located within and operating
within one of the two generally concentric tubes.
16. The device of claim 13, wherein the head encloses a first
adjustable flow control valve that defines the flow control device
in the first medium flow passage, the head also encloses a second
adjustable flow control valve that defines the flow control device
in the second medium flow passage, the first and second adjustable
flow control valves being adapted for separate adjustment, the
first adjustable flow control valve adapted to alter compression
characteristics and the second adjustable flow control valve
adapted to alter return characteristics.
17. The device of claim 10, wherein the pressurizing member
comprises an external container.
18. The device of claim 10, wherein the pressurizing member
comprises a piston that is pressurized by a volume of fluid, a
spring, an elastic member or an expandable bellows.
19. The device of claim 10, wherein the pressurizing member is
integrally formed between the outer leg of the front fork and the
removable compact unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. National Phase of International
Application No. PCT/SE2006/001187, filed Oct. 18, 2006, which is
based upon Swedish Patent Application No. 0502310-6, filed Oct. 19,
2005, each of which is hereby incorporated by reference in its
entirety and priority is claim to each of these applications.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a device for telescopic
fork legs, preferably on a motorcycle or bicycle, where the
telescopic fork leg comprises outer and inner legs and a damping
system with a piston and piston rod arrangement that is arranged
within these.
[0004] 2. Description of the Related Art
[0005] A front fork for a motorcycle or a bicycle can be subjected
to wheel speeds in the whole range of 0-10 m/s and stroke lengths
of up to 300 mm. In order to be able to absorb such high speeds and
such large strokes, great demands are made of the front fork. It
must be able to absorb forces and be strong, while at the same time
it must be able to handle a large flow of oil. It is also desirable
to have good control in the whole range of speeds and for the
damping to be adjustable. A compact and light system that can be
adapted to fit several different front fork dimensions also is
desired. Reference is made, for example, to patent U.S. Pat. No.
6,260,832, that shows a front fork of the type described above.
U.S. Pat. No. 6,260,832 does not, however, have the desirable
build-up of pressure that is described below.
[0006] Current systems can be represented by a damper of the De
Carbon type, see for example FR1055443A, and have a serial damping
force construction that is based on a principle of pressurizing two
locations in series in order to avoid cavitation or the admixture
of air into the damping medium. This system has limitations in that
the pressures in the two pressurizing locations must more or less
harmonize with each other, as the drop in pressure
(.DELTA.P1=P.sub.low-P.sub.mid, .DELTA.P2=P.sub.mid-P.sub.gas)
across the two pressurizing pistons should be greater than zero in
order not to create cavitation. See FIG. 1. Because the drop in
pressure across the piston is dependent upon the flow resistance
through the piston in combination with the force that acts on the
piston, the flow resistance, controlled for example by a shims
stack, can only be adjusted within a certain limited range, which
thus also results in a limited area of use for the damper. It is
then also necessary to dimension pistons, piston rod and damping
tubes so that the force absorption agrees with the pressures that
have been built up, in order to obtain the required damping. With
serial damping, the oil is forced through both of the valves in
series, which results in high flow speeds. With high flow speeds
and high piston speeds, the design of the pistons is limited in
order not to obtain an unwanted uncontrolled build-up of pressure
due solely to the flow resistance.
[0007] A system with parallel damping solves the abovementioned
problem. Examples of such dampers can be found in the patent
documents EP1505315A2 and EP0322608A2. The parallelism in the
damping arises through the damping medium being pressurized by two
pressurizing pistons that are arranged parallel to each other in
the damping chamber and in a space arranged outside the damping
chamber. The pressurized outer space is interconnected with both
the compression chamber and the return chamber. With parallel
damping, the pressure on the low-pressure side of the damping
piston is always as large as possible, irrespective of whether the
front fork is subjected to a compression or a return stroke. The
definition of the low-pressure side of the damping piston is the
side of the piston where the volume of the chamber increases. Due
to the fact that the pressure is never allowed to become zero on
that side, cavitation is prevented. This parallel arrangement also
means that the damper can be pressurized and the pressure, that is
the damping, can be adjusted without having to take into account
the drop in pressure across the piston(s). The increase in
pressure, as well as the increase in force, now takes place without
cavitation, irrespective of the setting.
SUMMARY OF THE INVENTION
[0008] The designs according to EP1505315A2 and EP0322608A2 are
adapted for shock absorbers that are not subjected to the same
forces and impacts as a front fork. A device is thus required for a
front fork that comprises adjustable parallel damping. It is also
advantageous if the device is able to be adjusted to suit different
front fork dimensions and can be used as a kit for modifying an
existing front fork.
[0009] A telescopic fork leg that is arranged and configured in
accordance with certain features, aspects and advantages of some
embodiments of the present invention may comprise an outer and an
inner leg and a damping system arranged within these. The damping
system comprises damping system components that are acted upon by
the flow of medium caused by the compression and expansion
movements of the main piston. The damping system components
together form a compact unit that comprises parallel medium flow
passages for the flow between the upper and lower sides of the main
piston and the flow that is caused by the pressurizing device that
pressurizes the whole damping system. The medium flow passages are
arranged parallel to each other in order to ensure low flow speeds
between the said sides of the main piston and thereby prevent the
uncontrollable build-up in pressure and force on the sides of the
piston as a result of the rapid movements and large strokes of the
front fork. In each damping system component, the flow through one
or both of the respective medium flow passages can be arranged so
that it can be adjusted or selected by means of devices, for
example valves, in order to achieve, for example, matching of the
damping characteristics to different types of terrain, by means of
an exceptionally wide range of settings. This wide range of
settings is achieved by the medium flow passages comprising
separate connections to a common pressure build-up location where
the pressure is created by the abovementioned pressurizing
device.
[0010] In accordance with certain features, aspects and advantages
of some embodiments of the present invention, the damping system
components comprise two concentric tubes in the form of a damping
tube and an outer tube that is arranged around the damping tube.
The tubes together form a portion of a removable insert system in
the front fork. The insert system creates a double tube function in
which the damping medium can flow in parallel as a result of the
duct between the damping tube and the outer tube being used to
connect together the two chambers and the common pressurizing
location. The pressurizing location is connected to the medium flow
passages between the damping cylinder and the outer tube via a head
that also comprises valves for adjusting the flow of the medium.
This insert system forms a compact unit that is simple to adapt to
different front fork dimensions and that can also be used as a kit
for providing an existing front fork with parallel damping.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other features, aspects and advantages of the
present invention will now be described with reference to the
drawings of some preferred embodiments, which embodiments are
intended to illustrate and not to limit the invention.
[0012] FIG. 1 shows a damper according to previously-known
technology (De Carbon)
[0013] FIG. 2 shows a front fork mounted on a vehicle
[0014] FIG. 3 shows a view of the front fork in cross section
[0015] FIG. 4 shows a detail view of a lower part of the front
fork
[0016] FIG. 4a shows a detail view of a hydraulic stop
[0017] FIG. 5a shows a simplified view of the front fork in cross
section with arrows illustrating the flow during a compression
stroke
[0018] FIG. 5b shows a simplified view of the front fork in cross
section with arrows illustrating the flow during a return
stroke
[0019] FIG. 6 shows another embodiment of the front fork with
internal pressurized bellows as a pressurizing device.
[0020] FIG. 6a is a detail view of a pressurizing device in the
form of a movable piston pressurized by gas.
[0021] FIG. 6b is a detail view of a pressurizing device in the
form of a movable piston pressurized by a spring.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] FIG. 2 shows a front fork mounted on a vehicle, in this
embodiment a motorcycle, of which only the front part is shown.
Fork legs (1) are arranged on each side of a steering pillar (2).
The lower parts of the fork legs (1) are attached to the wheel (3)
and the upper ends are connected to the frame (4) via the top yoke
and bottom yoke (5a, 5b). According to this embodiment, each fork
leg (1) of the front fork has an external pressure chamber (6a, 6b)
that is attached to the respective fork leg (1). Other fixing
locations for the pressure chamber are possible, for example in the
yoke, in the frame or on the steering pillar.
[0023] FIG. 3 shows the front fork in cross section and its
construction and function are described below in greater detail.
The front fork comprises a lower inner leg (7) arranged on a bottom
unit (8) and an upper outer fork leg (9) that terminates in a head
(10) that seals the fork. A spring (11) is arranged in the lower
inner leg (7) and the damping system is arranged in the upper outer
leg. The damping system is constructed of a damping tube (13) and
an outer tube (14) that together create a double tube construction
that contributes to parallel flow. A shimmed damping piston (15) is
arranged in the damping tube (13) on a piston rod (16), which
piston (15) divides the damping chamber into a return chamber (18)
and a compression chamber (17). During movement of the piston (15),
the return chamber and the compression chamber alternate in being
the high- pressure and low-pressure side.
[0024] At the upper end of the front fork, opposite to the bottom
unit, the double tube is attached to the sealed-off head (10) that
comprises valves (12, 12'). The valves (12, 12') can be used to
adjust the pressure in the damping system to take into account both
high and low speeds and both compression and return strokes. The
valves (12, 12') are connected via separate connectors to a common
pressurizing location comprising a pressurizing device (19). In
this embodiment, the pressurizing device (19) is a container (20)
divided by a piston (21) and pressurized by gas. A hose (22) is
coupled (e.g., with a threaded coupler) to one end of the
container. In the illustrated embodiment, the hose (22) connects
together the container (20) and the head (10) of the front
fork.
[0025] The damping tube (13) and the outer tube (14) together with
the head (10), a tube end (23) and the pressurizing device (19)
form an insert system that is simple to assemble and compact in
size. The insert system can be adapted to be mounted in existing
front forks on many different types of vehicles in order to obtain,
in a simple way, a system with the advantages of parallel damping
without having to buy a completely new product. With the compact
insert system, it is also easy to dismantle and service the
product.
[0026] One end of the piston rod (16) is attached to the bottom
unit (8) on the front fork and the piston (15) is mounted at the
other end. The piston rod (16) preferably is sealed against and
extends through the tube end (23) of the insert system.
[0027] FIG. 4 shows an enlarged partial view of the lower part of
the front fork. In order to support the piston rod at the joint, a
spring support (24) is arranged around the piston rod. The spring
support (24) fulfils two functions: giving the piston rod an extra
point of support and providing a low-friction surface for the
spring to move against.
[0028] A metallic part (25) is arranged at the end of the spring
support (24). This part (25) interacts with, that is can be
inserted into, a cylindrical part (26) that is attached to the
bottom unit (8), in such a way that a hydraulic stop is created,
which reduces the likelihood of the front fork bottoming in the
event of unusually strong compression.
[0029] The fact that the insert system is easy to dismantle from
the front fork is also illustrated by FIG. 4a, which shows the
lower part of the front fork. The figure shows that the lower part
(26a) of the hydraulic stop (26) is pressed into the bottom unit
(8) of the front fork by pressure force. A thread (26b) is arranged
in the internal diameter of the hydraulic stop, so that a bottom
part (27) can be screwed into the thread (26b). The bottom part
(27) also comprises a seal (28) that reduces the likelihood of
leakage from the front fork. The bottom-most part of the bottom
part (27) is designed to be able to be attached or to be screwed in
and out using a hexagonal key, so that the front fork is easy both
to assemble and to dismantle. A piston rod holder (28a) can be
integrated with the seal (28) that is threaded into this bottom
part (27). The piston rod (16) is attached in a recess in the
piston rod holder (28a) and the other part of the holder (28a) is
screwed down from above into the abovementioned bottom part (27).
Due to the fact that the holder (28a) can be screwed out of the
bottom part (27), the front fork is simple to dismantle by
withdrawing the whole insert in an upward direction.
[0030] FIGS. 5a and 5b show the flow in the front fork through
different medium flow passages (29, 30) and through flow areas that
are adjusted by valves (12a, 12b, 12a', 12b'). The valves comprise
high-speed valves (12a, 12a'), low-speed valves (12b, 12b') and
standard non-return valves (12c, 12c'). The different types of
valve are already well known and will not be described in greater
detail. The medium flow passages (29, 30) are arranged in such a
way that they are parallel in relation to each other and are
connected to the common pressurizing location, which comprises the
pressurizing device (19) in the illustrated configuration. Because
the passages (29, 30) are parallel, the flow is divided between the
two medium-flow passage areas and the flow speeds in the system can
essentially be reduced, for example halved, in relation to the
actual speed of the longitudinal displacement movements. The flow
speed in the medium is determined by the frequency of the movements
or the size of the impacts and, with a lower flow speed, which
greatly reduces the likelihood of uncontrolled build-up of pressure
and forces that can otherwise arise in the system.
[0031] The high-pressure and low- pressure sides of the damper
change with the direction of the stroke. As a result of the flow
paths and the position of the valves, the pressure on the
low-pressure side is always as high as possible and the likelihood
of cavitation is greatly reduced.
[0032] During a compression stroke, FIG. 5a, the damping medium
flows through the damping system as shown by the flow arrows in the
figure. The solid arrows represent the compression flow when the
front fork is subjected to a force with high speed and the broken
arrows represent the compression flow when the speed of the force
that is applied is low. That is, at high speeds, when parts of the
damping medium on the high-pressure side (H) are pressurized by the
shimmed piston (15), the remaining quantity of medium flows via a
passage (illustrated in a simplified form by (29)) in the head (10)
through the adjustable high-speed valve (12a) and the non-return
valve (12c') through the space between the tubes (13 and 14) to the
other side, that is the low-pressure side (L), of the piston. At
low speeds that do not cause sufficient pressure to open the shim
stack and the high-speed valve, the medium flows via the adjustable
low-pressure valve (12b) via the same non-return valve (12c') to
the low-pressure side (L). Pressurizing of the medium, by means of
the pressurizing device (19), takes place parallel with the flow.
The medium that is displaced by the piston rod (16) can be taken up
by the container or any other component, mechanism or volume that
acts as a pressurizing device (19).
[0033] During a return stroke, FIG. 5b, the damping medium flows
according to the same principle but in the opposite direction to
the compression direction described above, according to the flow
arrows shown in FIG. 5b. The flow is thus partially directed
straight through the piston (15) from the high-pressure side (H),
and partially up through the space between the tubes (13, 14), via
the passage (30) in the head (10), through the valve (12a' or 12b')
dependent upon high or low speed, through the non-return valve 12c
and then on to the low-pressure side (L) of the piston.
Pressurizing of the medium is also carried out here parallel with
the flow.
[0034] As the compression and return adjustments are separated, the
valves (12a, 12a', 12b, 12b', can be adjusted independently of each
other. The pressure therefore can be controlled in such a way that
the build-up is greatest during the return or compression stroke,
depending upon the external circumstances. The damping
characteristics can thus be maximally adapted to suit the terrain,
as a result of the large range of adjustment that the valves (12a,
12a', 12b, 12b') now have. The large range of adjustment of the
valves means an adjustment of the medium flow area from anywhere
between maximal and minimal area depending upon the damping force
characteristics that are desired.
[0035] With parallel passages (29, 30) described above, the flow
speed to a specific valve also can be reduced if the pressure on
this valve becomes critically high. As the damping medium will take
the easiest path (the lowest pressure) in the system, this
adjustment capability means that a wide range of pistons (15) and
pressurizing devices (19) can now be utilized. An advantage of this
is that larger pistons can be used and, with larger pistons, the
pressure does not need to be so high in the system and the damper
has a smoother characteristic. By a smoother characteristic is
meant that the increase in pressure, and also the increase in
force, can take place without cavitation, irrespective of the
setting.
[0036] FIG. 6 shows another configuration that is arranged and
configured in accordance with certain features, aspects and
advantages of some embodiments of the invention. The configuration
illustrated in FIG. 6 preferably does not use an external
pressurized container. In the illustrated embodiment, the front
fork also comprises a lower inner leg (7) arranged on a bottom unit
(8) and an upper outer fork leg (9) terminating with a head (10)
that is sealed against the fork and upon which head the damping
system is arranged. The valves (12, 12' (here drawn in a simplified
way)) are arranged in the sealed head (10) and ducts in the head
interconnect the pressurized spaces. The illustrated damping system
is constructed of a damping tube (13) and an outer tube (14) that
together form a double tube. A pressurizing part (19), for example
a floating piston or bellows, can be arranged in a divided space
outside the outer tube (14). The pressurizing part can comprise a
piston that is pressurized by a volume of fluid, a spring, an
elastic member or an expandable bellows, for example but without
limitation. The pressurizing part absorbs the volume of damping
medium that the piston rod (16) displaces during maximal
compression. The reverse side of the floating piston is pressurized
by gas (FIG. 6a), a spring (FIG. 6b) or the like and the bellows
are pressurized by a compressible gas or the like. Because the
whole damping unit can be removed, the gas pressure that
pressurizes the damper can also be adjusted in a simple way, for
example by having a filling valve (31) connected to the divided
space or to the interior of the bellows (not shown). The bellows
can, for example, be in the shape of a toroid that is sealed
against the surroundings or a cylinder sealed against any one of
the double tubes. As the pressurization of the illustrated front
fork does not use of an external container, the front fork is
easier to assemble and takes up less space.
[0037] Although the present invention has been described in terms
of a certain embodiment, other embodiments apparent to those of
ordinary skill in the art also are within the scope of this
invention. Thus, various changes and modifications may be made
without departing from the spirit and scope of the invention. For
instance, various components may be repositioned as desired.
Moreover, not all of the features, aspects and advantages are
necessarily required to practice the present invention.
Accordingly, the scope of the present invention is intended to be
defined only by the claims that follow.
* * * * *